Quartz lamps



United States Patent Inventor John Frederick Smalley London, England Dec. 6, 1967 Dec. 22, 1970 British Lighting Industries Limited London, England Feb. 6, 1967 Great Britain Appl. No. Filed Patented Assignee Priority QUARTZ LAMPS 6 Claims, 7 Drawing Figs.

U.S.Cl. 313/113, 3l3/5l.313/3l5,313/3181339/52 lnt.Cl. HOlk 1/24 Field of Search 3l3/49,50, 51,318,ll3,222,3l5;339/50,52,55,57

[56] References Cited UNITED STATES PATENTS 413,636 10/1889 Van Gestel 339/52X 2,763,803 9/1956 Krefft et a1 313/49 3,274,426 9/1966 Scoledge et al. 313/51X 3,286,118 11/1966 Vause etal. 313/318 3,012,167 12/1961 Poole 313/315X 3,341,731 9/1967 Wilson 313/318X F ORElGN PATENTS 701,916 1/1965 Canada 313/222 Primary Examiner-Raymond F. Hossfeld Attorneys-Owen J. Meegan and Laurence Burns ABSTRACT: An are or filament lamp having a quartz envelope with molybdenum foil seals in which the external leads are of molybdenum wire with a nonoxidizing coating of platinum and are made stiff enough, preferably in loop formation, to enable the lamp to be supported directly by electrical contacts engaging the leads, thus facilitating location of the lamp in a fitting.

PATENTED 032221970 SHEET 1 BF 2 Fig.6,

Fig.5.

AT ORNE JOHN FREDER ICK SMAL LEY INVENTOR PATENIEDnEc22|9m 35 49833 SHEET 2 BF 2 JOHN FREDERICK SMALLE'! INVENTOR m a W" TURN QUARTZ LAMPS The invention relates to electric lamps having a linear envelope of high-temperature glasssuch as fused silica or quartz. Typical lamps are high-pressure discharge lamps and tungsten halogen lamps.

These envelopes are generally formed from a linear tube of quartz which is sealed by pinching each end about a molybdenum foil.

Leads extend from the foils into the tube and support electrodes or a filament according to the nature of the lamp. Further leads, which are welded to the foils, extend outwards to supply current to the lamp.

In a conventional lamp design a cap of ceramic material is fitted to each pinch. The cap has anickel plate in the end furthest from the lamp and the lead is connected to this plate. The lamp is positioned in a fitting having opposed contact plungers so that the plungers are in contact with the nickel plates and grip the lamp. The caps may be designed so as to assist in the location of the lamp.

According to the present invention there is provided a lamp consisting of a bare linear tube of high-temperature glass sealed at both ends by pinches in which are embedded foils for providing current to the lamp, each foil having a stiff external lead of molybdenum or molybdenum alloy having a nonoxidizing surface which is adapted to engage a contact in a light fitting so that the lamp may be supported in the light fitting between opposed contacts.

Preferably the foil is of molybdenum or molybdenum alloy and the lead is constructed so as to provide a heat sink to prevent the foil oxidizing.

The external leads may be in the form of loops and the contacts they engage may be contact plungers between which the lamp is gripped or pairs of spring blades to hold the loops onto projections from which the lamp may be suspended.

The nonoxidizing surface may be provided by a coating of platinum or other material which does not oxidize at the operating temperature of the lamp.

An embodiment of the invention will be described with reference to the accompanying drawings in which:

FIG. 1 is a lighting unit comprising high-pressure mercury vapor discharge lamp constructed according to the present invention and mounted within a light fitting,

FIG. 2 shows the mounting of the arc tube of FIG. 1 within the light fitting having one form of contact.

FIG. 3 is an end view of anarc tube mounted within a fitting having a second form of contact,

FIG. 4 is a plan view of FIG. 3, and 4 FIGS. 5-7 show three forms of lead constructed according to the invention.

In FIG. I there is shown a high-pressure mercury vapor lamp 21 mounted within a light fitting 2 having a surface in the form of a parabolic reflector. The lamp consists of a bare linear arc tube 3 of high-temperature glass, such as fused silica (quartz), and of about 14mm. diameter which is sealed at each end by a pinch 4. The arc tube typically contains mercury and a small quantity of metal iodides.

A shown more clearly in FIG. 2 a foil 5 of molybdenum (or molybdenum alloy) is embedded in the pinch to provide current to the lamp.

A tungsten electrode 6 is welded to each foil, the electrodes extending within the arc tube to support a discharge. Each foil has a lead 7 welded to the foil and projecting from the end of the pinch 4. The lead is a stiff loop of platinum-clad molybdenum of 0.030 inches diameter. The molybdenum may be replaced by a molybdenum alloy which has a sufficiently high melting temperature to enable it to be used in such lamps and which has suitable mechanical properties. Since a direct electrical contact is to be made with the lead its surface must be of a material which does not oxidize at the operating temperature of the lamp. Since molybdenum does oxidize at this temperature a coating of a nonoxidizing material, such as platinum, is necessary. The lead should be constructed to provide a heat sink to prevent oxidation of the foil.

Various forms of loop are shown in FIGS. 5 to 7, but the loop may be replaced by a stiff rod or other extension.

As shown in FIGS. 1 and 2, the loop :is adapted to sit on the end of a conventional, spring-braced suitably-shaped contact plunger 8 in the fitting I. As a lamp is being inserted, plunger 8 retracts into space 12 to allow for the extra length. When mounted, plunger 8 then moves forward again to provide electrical contact with lead 7. The end of the plunger may contain a slot shaped to match the loop or it may be in the form of a concave dish. The lamp is fitted between the opposed plungers 8 which grip it firmly with the electrodes accurately aligned without need for further prefocussing and locate the lamp at the focus of the parabolic reflector. We have found that the use of the invention enables accurate optical settings to be obtained in fittings. A conventional source of power is connected to the ends of connectors 13. A modified form of contact shown in FIGS. 1 and 2 is illustrated in FIGS. 3 and 4. FIGS. 3 and 4 show one side of the contact which consists of two spring blades 9 and 10 arranged one above the other with a projection 11 on the upper face of the lower blade 10. Pairs of spring blades are mounted at each end of the light fitting to replace the contact plunger and are connected to a current source in the same manner. The lamp is mounted in the fitting by inserting the loops 7 between the blades so that the loop passes round the projection. Each loop is then held securely by a pair of blades and the lamp is suspended from the loops.

- Leads may be fitted to tungsten halogen lamps, or any other bare linear quartz lamp in the same way and the same mounting may be used.

I claim:

1. A lamp having a bare linear tube of high temperature glass: 4

said tube having a pinch seal at each end, an electricallyconducting foil embedded in each of said pinch seals;

light-generating means within said tube, means electrically connecting said light-generating means with said foils; and

two stiff electrically-conducting external leads of molybdenum or molybdenum alloy having a nonoxidizing surface. said external leads being in the form of loops, both ends of the loops being attached to the foil, said external leads being attached one to each of said foils and extending outside said tube to support the lamp in a fixture.

2. A lamp as claimed in claim 1 wherein said external leads have a coating of platinum forming said nonoxidizing surface.

3. A light source comprising: a light fitting, a lamp having a bare linear tube of high temperature glass, said tube having a pinch seal at each end, and an electrically-conducting foil embedded in each of said pinch seals; light-generating means within said tube; means electrically connecting said lightgenerating means with said foils; two loop-shaped stiff electrically-conducting external leads of molybdenum alloy having nonoxidizing surfaces, said external leads being attached one to each of said foils and extending outside said tube to support the lamp in said light-fitting means for mounting said lamp in a predetermined position relative to said] fitting, said mounting means comprising electrical contact means engaging the extemal leads of the lamp and supporting said lamp by said leads.

4. A light source as claimed in claim 3 wherein said light fitting includes a parabolic reflector having a focus and said lamp is located at said focus.

5. A light source as claimed in claim 3 wherein each of said external leads is in the form of a loop and said contact means comprise two contacts recessed to fit the ends of said loops, at least one of said contacts being a spring-loaded plunger.

6. A light source as claimed in claim 3 wherein each of said external leads has the form of a loop and said contact means comprise two pairs of spring blades, each of said loops lying between a pair of blades and one of said blades having a retaining projection lying within said loop. 

